Multiple heating rate kinetics

The kinetics of the cure of ATS at 130°C in nitrogen determined by various methods are shown in Figure 1. The dashed curve represents the prediction based on kinetic parameters determined by analysis of scanning DSC data by the method of multiple heating rates described previously (8). This method utilizes a rate equation of the form ... 

Fig. 9. Master cure curve for polyurethane pultrusion resin system. Data points from isothermal DSC and DSC simulated cure profiles were shifted to times at 80°C by means of equation 14 using the activation energy measured from multiple heating rate DSC. The solid line is calculated from the second-order kinetic equation found to fit the master...

Kinetic analyses of multiple nonisothermal, also referred to as multiple heating rate, runs are most commonly performed by using the methods of Friedman, Ozawa, and Flynn and Wall. However, application of the Kissinger method (Kissinger 1957) is discouraged because the method yields a single value of... 

TGA Isothermal or non-isothermal analysis Constant or multiple heating rates Thermal and/or oxidative stabilities and compositional properties Decomposition temperature (thermal stability) Percentage of mass loss and residue Temperature of thermal degradation beginning, maximum and total decomposition Total mass loss Activation energies evolution Kinetic models... 

Concerning the nature of electronic traps for this class of ladder polymers, we would like to recall the experimental facts. On comparing the results of LPPP to those of poly(para-phenylene vinylene) (PPV) [38] it must be noted that the appearance of the maximum current at 167 K, for heating rates between 0.06 K/s and 0.25 K/s, can be attributed to monomolecular kinetics with non-retrapping traps [26]. In PPV the density of trap states is evaluated on the basis of a multiple trapping model [38], leading to a trap density which is comparable to the density of monomer units and very low mobilities of 10-8 cm2 V-1 s l. These values for PPV have to be compared to trap densities of 0.0002 and 0.00003 traps per monomer unit in the LPPP. As a consequence of the low trap densities, high mobility values of 0.1 cm2 V-1 s-1 for the LPPPs are obtained [39]. 

Multiple scan DSC curves at various heating rates were utilized to obtain kinetic parameters for an acetylene terminated sulfone (ATS) which were compared with isothermal reaction rates. The comparison between scanning and isothermal reaction kinetics illustrated the retarding effect of incipient vitrification of the ATS on the reaction rate. 

Table 2. The kinetic parameters for the three-step thermal degradation of PE and PE-n-MMT as obtained by the multiple-curve analysis of the experimental TGA-data (heating rates 3,5,10 and 20 K/min) in frames of the reaction model...

Popescu is a non-model kinetic analysis method which is based on multiple scanning rates two temperature values T = and T = will determine a pair of values of a on each curve of different heating rate (a l, (a ,3, a ), and also... 

Table 2. Kinetic parameters resulting from multiple-curve analyses (heating rates 3,5 and 10 K/min) with reaction model (A—>X/—from TG measurement of neat...

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